The dedication in British writer Gerard Woodward's debut novel, August, was "To the memory of my mother". The book, the first of what has become known as the Jones trilogy, is a tender, moving and droll fictionalised account of his own family. His parents have been recast as Aldous and Colette Jones, with children Janus, James, Juliette and Julian. Janus represents Woodward's oldest brother, Francis, and Julian is the young Gerard.

August spans a downward spiral from August 1955, when Colette was a happy young London housewife, through to August 1970, by which time the Joneses have been pulverised by poverty, alcoholism and mental illness. But it gets even stranger, for Colette/Woodward's middle-class mother had a taste for something else.So it has to be asked: "Did your mother sniff glue?"

"Yeah. Oh, yeah," says Woodward, on the phone from Frome, near Bath, where he teaches creative writing at Bath Spa University. "No one had heard of it. As far as we knew she was the only person in the world doing it. This was in the mid-to-late-60s and it didn't really become a phenomenon until the 70s in Britain."

August was published to great acclaim in 2001, followed by I'll Go To Bed At Noon, which was shortlisted for the 2004 Man Booker Prize, and A Curious Earth in 2007. An Observer critic called the trilogy "vigorously dismaying", and Woodward has described his mother as "a piano-playing drug addict; literary, but debauched".

Woodward, who was 40 when August came out, struggled for years with how to process the story of his family; his older brother Francis (Janus) was very smart and a musical prodigy but he was also an unstable, violent alcoholic who died in 1981 after being hit by a train while drunk. It was possibly a suicide. His mother died of alcohol poisoning a year later, and his father died in 1991.

Woodward doesn't like the trilogy to be described as "semi-autobiographical", preferring "dumplings of fact in a fictional stew". After attempting unsuccessfully to write the story in the form of a book-length poem, he won a Somerset Maugham Award which took him to Vietnam and gave him time to think about what he needed to do. He had the material; he just needed the form.

"I think writing it as a novel rather than an autobiography made it a lot easier," he says.

"In a sense I was writing about fictional characters. It sticks closely to the story of what really happened but, even just by giving them different names, made it a lot easier to write. Once I started writing it, I became concerned with novelistic things and making it a good story and making the characters believable. That is probably why I took a long time to get around to writing it, because I was worried I wouldn't get the whole complexity, that I would misrepresent them.

In the books, Janus becomes more and more brutally contemptuous of his spaced-out mother. Is that what Francis was like?

"Yes, that's how I remember him," says Woodward. "But I was wanting to get all the qualities across. He wasn't just an alcoholic, not just a rebel. He was also very charming and funny and very clever. I have a box of documents from Francis, some of which are reproduced in I'll Go To Bed At Noon. They are a strange mixture of things like receipts, county court judgments, arrest warrants, school homework. He was in court lots of times, mainly drunk and disorderly. Eventually, he went to prison for threatening to kill his boss, more or less as it happened in the novel."

Woodward left school when he was 16, convinced the world was on the brink of a nuclear war. He had a "series of jobs", leaving home the week after his mother died, then went to Falmouth Art School, where he admirably ended his first year with a project that involved a huge pile of rubbish topped with a sausage roll. He was advised to take time off.

"Yeah, I was quite pleased with that," he laughs. "It caused a stir, which is what I wanted."

He completed a social anthropology degree in London, then started post-graduate studies in Manchester before abandoning that for a job filling vending machines at the university for four years. He liked that job.

"Then August was published and that enabled me to leave," he recalls. "I worked freelance for a few years when I wrote the second and third novels and then the post came up at Bath Spa. I like teaching [his father was an art teacher] and I like having a steady income, so it has worked out really well."

Woodward's latest novel, Vanishing, centres around a "camouflage artist" called Kenneth Brill, charged with being a spy for painting landscapes in the Heathrow area during World War II when the airport was being planned. During the long process of interrogation, incidents from Brill's life from childhood into adulthood emerge that cast him as a person of dubious character. But it's all about context.

"He has been described as naive," says Wood-ward. "I didn't know in advance what he had done and I played with it. What I wanted to do was have a character who wasn't sure himself whether he was a good person or a bad person. I set up various situations where his actions could be interpreted in different ways."

Brill is confused about many things in his life, not least his sexuality. He is so suppressed that when he goes to Slade Art School and attends life classes, he vomits or faints every time he sees a nude male model. Like Woodward, his academic art career doesn't last long.

Brill's early childhood is based near the village of Heathrow, once one of the most productive agricultural regions in Britain. Although the title of Vanishing can be applied to the opaqueness of Brill's personality, it also applies to Heathrow itself, acquired under wartime powers under the pretext that the authorities needed to build a military airport.

"That was never actually the plan," he says. "It was always to build a civil airport. There was very little compensation and it was all very rushed so all these people who had been living on the land for generations suddenly had to move."

It's a fine, intriguing novel but the Jones trilogy haunts me. Like them, this new novel also contains a dedication, but thankfully these days it's to his wife: "To Suzanne, for Vanishing, and for not vanishing." He met Suzanne at Falmouth Art School. At least he got something positive and lasting from that tumultuous time.